ground

ground, in electricity, electrical contact with the Earth, which remains essentially at a constant potential. A grounded wire on a lightning rod leads large electric charges from the atmosphere directly to Earth, preventing them from taking other paths that might result in damage to property or injury to persons. Since people are themselves often grounded (standing on a moist basement floor or leaning against, or otherwise in contact with, metallic plumbing), interior wiring systems have one wire connected to ground to minimize accidents to persons and fire damage in case of lightning, transformer failures, or insulation breakdown in wiring. Metallic boxes and other conductor enclosures are grounded, so that even in case of insulation breaks any parts that can be touched will be at ground potential and unable to give shock. Portable electrical appliances are frequently provided with a grounding connection to minimize danger of electric shock.